7. Anatomy of the breast

Question 1

What is the breast comprised of?

Answer 1

Glandular, fat and fibrous tissue

Question 2

Describe embryology of the breast

Answer 2

Derived from precursor ectoderm cells during week 4
Form mammary bud by week 5
Background breast stroma develops throughout gestation
>12 weeks, secondary buds lengthen and branch forming a complex network of radially arranged breast ducts that connect the nipple with the mammary lobules

Question 3

Where does the breast extend from?

Answer 3

Between 2nd and 6th rib spaces, from caudal to cranial

From lateral border of sternum to mid-axillary line

Question 4

How are breasts split?

Answer 4

Into 4 quadrants

Upper/Lower and Inner/ Outer

Question 5

Where does the majority os tissue lie compared to the remaining breast?

Answer 5

Upper outer quadrant

Question 6

How many ductal lobular units are in the breast? Where do they drain?

Answer 6

15-20 ductal-lobular units

Each drains into a main duct

Question 7

What lies interspersed between ductal lobular units?

Answer 7

Fat

Question 8

What structures divide the ductal lobular units?

Answer 8

Fibrous septae that radiate from the centre outwards

Question 9

What holds the breast?

Answer 9

Suspensory ligaments of Cooper (Coopers ligaments)

Question 10

How many milk ducts are there in the breast?

Answer 10

4-18

Question 11

Describe the blood supply to the breast

Answer 11

Branches of the:
Lateral thoracic artery
Internal thoracic artery
Thoracoacrominal artery
Thoracodorsal artery
Intercostal arteries

Question 12

What are the 3 principle groups of veins draining the breast?

Answer 12

Perforating branches of the internal mammary vein
Tributaries of the axillary vein
Perforating branches of the posterior intercostal veins

Question 13

Describe the main innervation to the breast

Answer 13

Anterolateral and anteromedial branches of thoracic intercostal nerves T3-T6.
Also innervation from the supraclavicular nerves to the upper and lateral parts of the breast.

Question 14

Describe innervation to the nipple

Answer 14

Dominant supply from the lateral cutaneous branch of T4.

Question 15

Where does the predominant lymphatic supply come from?

Answer 15

The axila

Question 16

What are the 5 groups of axillary lymph nodes?

Answer 16

Humeral
Subscapular
Pectoral
Central
Apical

Question 17

Describe % of drainage of the breast

Answer 17

75% of breast drains to lymphatics in axilla

25% of breast drains to lymphatics in Internal Mammary nodes

Question 18

Level 1 lymph nodes in pyramidal space

Answer 18

Lateral to pec minor

Question 19

Level 2 lymph nodes in pyramidal space

Answer 19

Posterior to pec minor

Question 20

Level 3 lymph nodes in pyramidal space

Answer 20

Medial to pec minor

Question 21

Lymphatic drainage of breast and axilla

Answer 21

Pyramidal compartment, tightly invested between the upper extremity and thoracic wall, 4 boundaries:
Medially: Serratus Anterior
Laterally: Intertubercular groove of humerus
Anteriorly: Pectoralis Major and Minor
Posteriorly: Teres Major, Subscapularis + Latissimus Dorsi

Question 22

Why do surgeons have to be careful when extracting lymph nodes?

Answer 22

Long thoracic nerve: damage results in winging of scapula
Thoraco-dorsal pedicle nerve: damage results in reduced power when lifting arm above head
Intercostal brachial nerves: Damage results in loss of sensation to upper inner aspect of arm

Question 23

Sentinel node biopsy

Answer 23

Mapping procedure.

Remove first 2-4 lymph nodes that drain breast cancer to the axilla.

Question 24

Breast cancer lymphoedema

Answer 24

Puffy swollen arm, debilitating

Occurs 2-3 years after lymphatics have been removed in surgery.

Question 25

Lymphoedema

Answer 25

Abnormal, generalized or regional accumulation of protein rich interstitial fluid
Oedema formation and change in tissue architecture
Reduction in lymphatic transport capacity from arm with an increase in lymphatic load

Question 26

Risk factors for lymphoedema

Answer 26

Axillary surgery
Radiotherapy
Chemotherapy
High BMI
Infection/ trauma

Question 27

Strategies to reduce lymphoedema

Answer 27

Less axillary surgery
Axillary reverse mapping (ARM)
LYMPHA

Question 28

Axillary reverse mapping

Answer 28

Discriminate lymphatics that drain the arm from the lymphatics that drain the breast
Aims to identify and preserve nodes and/or lymphatics draining from the arm during ALND, thereby minimizing arm lymphedema

Question 29

Congenital abnormalities affecting breast

Answer 29

Underdevelopment/ absence of 1 breast (may coexist with muscle/ribcage anomaly) = Poland syndrome 
Accessory nipples (polythelia) 
Absent nipples (athelia)
Accessory breast tissue
Tubular breast defomity